I. Field of the Invention
The present invention relates generally to cover assemblies and, more particularly, to a cover assembly for a ground opening, such as a manhole or a storm drain.
II. Description of the Prior Art
The previously known cover assemblies for ground openings, such as manholes and storm drains, typically comprise a frame constructed of cast iron. The cast iron frame includes a circular opening adjacent its top. The frame is secured to the underground concrete manhole or storm drain construction by either cementing it or bolting it into place.
These previously known frames include an annular abutment surface adjacent their upper end. A manhole cover or storm drain cover is then positioned into the frame so that the annular abutment surface contacts and supports the cover adjacent the top of the frame. The manhole cover and storm drain cover (hereinafter collectively referred to as manhole cover) are also conventionally constructed of cast iron.
These previously known cover assemblies suffer several disadvantages. One primary disadvantage of these previously known assemblies is that the cover and/or frame may distort slightly after long exposure to both the elements and physical abuse. Since both the cover and the frame are constructed of cast iron, such distortion may cause the cover and frame to seize together. Once the cover and frame have seized together, the removal of the cover from the frame is not only time consuming, but it may be even necessary to destroy the cover and replace the cover with a new one.
A still further disadvantage of these previously known cover assemblies, and particularly manhole cover assemblies, is that the manhole cover must be at the same level as the street level. After time, however, many streets are repaved or resurfaced with asphalt which raises the level of the street, typically by one and one-half inches.
Once the level of the street has changed, it is often necessary to replace the entire manhole assembly. This procedure, of course, is not only time consuming but also very expensive. There have, however, been some manhole cover assemblies with means to adjust the vertical heighth of the manhole cover, but these manhole cover assemblies with such adjustment means are expensive and have not gained widespread acceptance.